The galaxy alignment effect in Abell 1689: evolution, radial and luminosity dependence

TL;DR

This study investigates galaxy alignments in Abell 1689, revealing stronger alignments in the inner regions and among fainter galaxies, supporting a tidal locking origin of the effect.

Contribution

It provides the first detailed analysis of galaxy alignment dependence on radius and luminosity in Abell 1689 using Hubble data.

Findings

Alignments are significant within 500 kpc of the cluster center.

Fainter galaxies show stronger alignment signals.

Bright galaxies are generally unaligned.

Abstract

We measure alignments on scales of 1 Mpc $h^{-1}_{71}$ for galaxies in Abell 1689 ($z=0.18$) from an existing Hubble Space Telescope mosaic. We find evidence of galaxy alignment in the inner 500 $h^{-1}_{71}$ kpc. The alignment appears to be stronger towards the centre and is mostly present among the fainter galaxies, while bright galaxies are unaligned. This is consistent with a model where alignments originate from tidal locking.